Pressure accumulator and motor control



July 3, 1956 F. JASEPH PRESSURE ACCUMULATOR AND MOTOR CONTROL Filed Nov.15. 1951 /w L, (z a t Q \N.mgmxi f/ e W PRESSURE ACCUMULATOR AND MOTORCONTROL Lawrence F. Jaseph, Memphis, Tenn., assignor to DoverCorporation, a corporation of Delaware Application November 15, 1951,Serial No. 256,497

S Claims. (Cl. 60-51) My invention relates generally to pressureaccumulators, and more particularly to an improved pressure accumulatorincorporating means for controlling the operation of a pump drivingmotor to maintain a predetermined pressure in a hydraulic system. p

In many types of apparatus, such as hydraulic lifts and elevators, it isdesirable to maintain a predetermined pressure in the system and toprovide a pressure accumulator having substantial displacement so as tohave available a supply of oil under pressure for sudden demands.

It is therefore an object of my invention to provide an improvedpressure accumulator for use in hydraulic systems, which also operatesas a control for the energization of the pump driving motor, and whichhas provisions for relief of the pressure in the system when excessivelyhigh pressures are attained.

Other objects will appear from the following description, referencebeing had to the accompanying drawings, in which- Fig. l is a centralvertical sectional view of the pressure accumulator;

Fig. 2 is a left end elevational View thereof; and

Fig. 3 is a diagrammatic view of the pressure accumulator and associatedparts of the hydraulic system, together with a schematic circuit diagramof the motor control circuit.

The pressure accumulator comprises a closed end cylinder 10 providedwith a head 12 secured to one end thereof by cap screws 14 and defininga passageway into the cylinder. The cylinder 10 is provided with a largebore 16 and a slightly smaller diameter bore 18. The cylinder end head12 may be secured to any suitable support, such as the top of areservoir 20, by cap screws 22. A piston 24 is provided with an annularend face packing 26 positioned in a suitable groove 28. The piston 24and cylinder 10 together define an expansible chamber adjacent the head12. The piston 24 has a long skirt portion 30, the lower portion ofwhich is externally tapered to form a camming surface 32 for cooperationwith a roller 34 suitably journaled on the end of a leaf spring actuator36 for cooperation with the operating plunger 38 of a limit or controlswitch 40. This switch is mounted within a suitable conduit box 42 whichis secured to the cylinder 10, the cylinder 10 having an opening 44through which the actuating leaf spring protects. The piston 24 has agroove 46 for an O-ring packing 48. An over pressure relief port 47 inthe cylinder 10 is connected to the reservoir 20.

The piston 24 is urged to the left by a relatively heavy coil spring 50which is compressed between the inside of the piston and a spring seat52, the position of which may be adjusted by means of a screw 54, theseat being held in adjusted position by a lock nut 56.

As best shown in Fig. 3, the apparatus may form part of a hydraulicsystem comprising the reservoir 20, an inlet pipe 58 for a pump 60, theoutlet of which is provided with a check valve and is connected to a T62. The T is connected to the head 12 by a nipple 64 and is connected tothe hydraulically operated apparatus by a pipe 66.

As diagrammatically illustrated in Fig. 3, the pump is driven by anelectric motor 68 connected in `series with a normally open controlrelay contactor CR-l to the poles of a double pole single throw switch70 by which the circuit is connected to the power lines L1 and L-2. Theswitch 40 is connected in series with the control relay coil C. R.across the poles of the switch 70.

The switch 40 is of a type which is normally closed and which opens witha snap-action upon a predetermined inward movement of the plunger 38,but which does not close until the plunger has moved outwardly aconsiderable distance beyond the point at which it was effective toclose the switch.

In operation, upon closure of the switch 70, the motor 68 will beenergized because the switch 48 is closed and relay C. R. will beenergized to close contactor CR-l, which forms part of the relay C. R.The pump therefore commences supplying oil from the reservoir 20 to thehydraulic apparatus connected to the pipe 66, and also supplies oilthrough the head 12 into the bore 16. As the pressure builds up, thepiston 24 will move to the right and the camming surface 32 on the skirtof the piston engages the roller 34 and at the predetermined pressureopens the limit switch 40. Opening of the limit switch 40 deenergizesthe control relay C. R., which permits the switch CR-1 to open, therebycutting off the supply of current to the motor 68.

When, due to the operation of the hydraulic apparatus connected to thepipe 66, the pressure in the cylinder 16 is reduced, the spring 50 willforce the piston 24 to the left. Considerable travel in this directionis permitted before the switch 40 snaps closed so that a substantialquantity of the hydraulic fluid may escape from the high pressure sideof the system before the switch 40 is closed. When this switch isclosed, the control relay C. R. is encrgized and its contactor CRl isagain closed to complete the motor energizing circuit.

If for some unforseen reason the pressure within the system shouldbecome excessively high, the piston 24 will be moved sufficiently to theright that its sealing packing 26 will uncover the port 47 and permitreturn of oil to the reservoir 22 through the conduit 49.

The pressure at which the switch 40 is operated may be adjusted by meansof the adjustment screw 54 so as to vary the degree of initialcompression of the spring 5t?. By virtue of the difference in positionsof the plunger at which it opens and closes switch 40, there will besubstantial travel of the piston 24 to the left from the position atwhich it opens switch 40 to the position at which it closes this switch,and unduly frequent cycles of operation are thereby avoided.

While I have shown and described a preferred embodiment of my invention,it will bc apparent that numerous variations and modifications thereofmay be made without departing from the underlying principles of theinvention. I therefore desire, by the following claims, to includewithin the scope of the invention all such variations and modificationsby which substantially the results of my invention may be obtainedthrough the use of su bstantially the same or equivalent means.

I claim:

1. In a pressure accumulator and motor control for a hydraulicapparatus, the combination of means forming a cylinder, a pistonreciprocable within the cylinder and having a skirt portion, a limitswitch having an actuator cooperable with the skirt portion of thepiston, a spring compressed between the piston and one end of thecylinder, means connecting the other end of the cylinder to thehydraulic apparatus, an electric motor, a pump operated thereby andhaving its outlet connected to the hydraulic apparatus., and a controlcircuit including Said switch for causing deenergization of the electricmotor when the spring has been compressed to a predetermined extent andthereafter to vcause'I reenergizatien .of the moror after said springhas expanded to cause the discharge. of a. substantial volume ofhydraulic uid trom ythe cylinder to the hydraulic apparatus.

2. A iluid' pressure accumulator and over pressure relief apparatuscomprising, means forming a cylinder having in its side a relief portand an opening and having an inlet opening at one end thereof, a pistonreciprocable in the cylinder, said piston having a tapering shirtportion, a spring. compressed between the Vpiston and one end of thecylinder vto urge the piston toward' the end of the cylinder having the.inlet opening, said Vpiston preventing liowy of luid from the inletopening to chev port until a predetermined pressure has been ,exceededso that the face of the piston uncovers the port, a limit switch securedto the cylinder means and having an actuator extending through the sideopening and engaged by' the skirt portion of the piston when apredetermined pressure. is ex ceeded, whereby the limitv switch may beused `for con'.- trolling the energization of a motor driven pump:supplying fluid under pressure to the inlet. opening of the accumulatorcylinder.

3. In a iluid pressure accumulator apparatus, including a cylinderhaving an opening in its side and art inletv opening at one end thereof,a piston reciprocable in the cylinder, a spring compressed within thecylinder to urge the piston toward the inlet opening, and .electricallyoperated means for supplying fluid under pressure: to the: inletopening, the combination comprising a tapering skirt portion integra-lwith the piston, and a switch secured adjacent the cylinder and havingan actuator extending through the side opening to engage the skirtportion-,of the piston when a predetermined pressure `is exceeded,whereby the limit switch may he .used to open the elec.- trical circuitand to stop the supplying of uidunder pressure. to the inlet opening ofthe. accumulator cylinder.

.4. In iluid pressure accumulator and over pressure relief apparatus,including a cylinder having in its side a port and an opening and havingan inlet opening at one end thereof, a piston reciprocable in thecylinder, a spring compressed Within the cylinder to urge the pistontoward the inlet opening, and means for supplying fluid under pressureto the inlet opening, the combination comprising, valve means formed bysaid piston for preventing iiow of uid from the inlet opening to theport until a predetermined .pressure in `the cylinder has been exceeded,a tapering skirt portion integral with thepistou., a limit switchsecured adjacent the cylinder and having an actuator extending throughthe. side opening, and' a roller on the actuator positioned forengagement with the skirt portion of the piston when a predeterminedpressure is exceeded, whereby the limit switch may be used to stop thesupplying of uid to the inlet opening of the cylinder.

5. A combined iluid accumulatora-nd control for a pressure'iiuid system,comprising, in combination, a cylinF der, means deiining a iiuidpassageway communicating with said cylinder, apifston slidahly mountedwithin said cylinder and having a tapered rear portion thereon, springmeans urging saidpiston. toward said passageway, a snap switch mountedonsaid cylinder, and an actuator on said switch positioned to beoperatedby said tapered portion of said piston upon movement of said pistonagainst said spring to. a predeterrnined position.

.References Cited inthe. le of this patent UNlT-ED STATES PATENTS829,845 Corey Ang,..28, 1906 1,543,841 Grigoleit. I June. 4, 19251,895,131 Leonard ..-..v Jan.A 2.4,. 193.3 2,277,569 Vickers Mar. 24,19,42 2,279,176 Pardee.. L.. Apr. 7, 1942 2,356,506v Davis Aug. 22,194.4

